"It was fast and erratic and the wind was pushing it, accelerating the fire," he said.

"The carpet guy started to move some of the carpet. It (the fire) got one of them (the rolls) at the end and melted a few others.

"The flames were probably six metres high."

A wire fence separates the delivery area from the rail corridor.

At this stage it is unclear whether the fire began in the delivery area or in the rail corridor.

The fire in being fanned by a strong breeze and a large number of emergency services works are on site, as well as detectives.

NSW Trainlink has advised that at least one train will be delayed at Wollongong “due to a bushfire near the line”.

The southbound track remains open, and all trains will be run along that track. Passengers are advised to listen for announcements and expect delays.

Update, 2.15pm: John Balzan, Fire and Rescue NSW Unanderra incident controller, said the fire was believed to have begun behind some skip bins.

"There's nothing to suggest it was malicious. It could have been a lit cigarette that someone might have had after work or during a lunch break and accidentally started the fire because it’s a hot day,” he said.

“Also, there could have been some materials there that combusted from the heat, just depending whether or not there were any containers that might have had a type of accelerant.

“We've determined that the fire started behind the bins in the premises, then has spread out towards the train line.”

The fire was travelling up the rail corridor when firefighters arrived.

The train line was re-opened after only a short closure.

Mr Balzan said crews had the blaze under control as at 2pm.

“[Carpet] contains the heat it keeps the heat trapped for some time, so we've got the owner using a forklift to remove some of the carpet so we can get water in each layer,” he said.